ESBL

ESBL
Name	Extended-spectrum beta-lactamase
Synonyms	ESBL
Field	Infectious diseases, Microbiology, Epidemiology
Symptoms	Dependent on site of infection
Complications	Sepsis, Treatment failure, Mortality rate
Causes	Bacteria carrying ESBL genes
Risks	Hospitalization, Antibiotic use, Urinary catheter
Diagnosis	Antimicrobial susceptibility testing, Polymerase chain reaction
Treatment	Carbapenem, Ceftazidime/avibactam, Plazomicin
Prevention	Infection control, Antimicrobial stewardship
Frequency	Increasing globally
Deaths	Contributes to Antimicrobial resistance mortality

ESBL. Extended-spectrum beta-lactamases are enzymes produced by certain Bacteria that confer resistance to a broad range of Beta-lactam antibiotics, including penicillins, cephalosporins, and the monobactam aztreonam. These enzymes are a major mechanism of Antimicrobial resistance and pose a significant challenge in both Hospital and Community settings, leading to difficult-to-treat infections. The genes encoding these enzymes are often located on Plasmids, facilitating rapid spread among bacterial populations.

Definition and mechanism

ESBLs are a diverse group of Beta-lactamase enzymes that hydrolyze and inactivate Beta-lactam antibiotics. They evolved from narrower-spectrum beta-lactamases like TEM-1 and SHV-1 through mutations that expanded their substrate profile. The primary mechanism involves the cleavage of the Beta-lactam ring, a core structural component of these antibiotics, rendering them ineffective. Most ESBLs belong to the Ambler molecular classification Class A and are inhibited by Beta-lactamase inhibitors like Clavulanic acid. The genes responsible, such as those from the CTX-M, TEM, and SHV families, are frequently carried on mobile genetic elements like Plasmids and Transposons, which promotes horizontal gene transfer between different bacterial species.

Epidemiology and risk factors

The epidemiology of ESBL-producing organisms has shifted dramatically since the 2000s, with CTX-M-type enzymes now dominant worldwide, replacing TEM and SHV variants. Major clones include Escherichia coli sequence type ST131 and Klebsiella pneumoniae ST258. High prevalence areas include Asia, South America, and parts of Europe, with increasing reports from the United States and Africa. Key risk factors for colonization or infection include prolonged Hospitalization, especially in Intensive care units, prior use of broad-spectrum Cephalosporins or Fluoroquinolones, presence of Urinary catheters or other invasive devices, and residence in long-term care facilities. International travel to high-prevalence regions is also a recognized risk factor for community acquisition.

Detection and diagnosis

Accurate detection is critical for infection control and appropriate therapy. Phenotypic methods include Antimicrobial susceptibility testing using Clinical and Laboratory Standards Institute or European Committee on Antimicrobial Susceptibility Testing guidelines, with key indicators being resistance to Ceftazidime, Cefotaxime, or Ceftriaxone that is reversed by Clavulanic acid in a Combination disk test or Double-disk synergy test. Automated systems like VITEK or BD Phoenix often include ESBL detection panels. Molecular confirmation utilizes Polymerase chain reaction and DNA sequencing to identify specific genes like blaCTX-M, blaTEM, and blaSHV. Laboratories may also employ Chromogenic agar for screening surveillance cultures.

Clinical significance and infections

ESBL producers are associated with increased Morbidity and mortality, longer Hospital length of stay, and higher healthcare costs. They are common causes of Urinary tract infection, Bloodstream infection (bacteremia), Intra-abdominal infection, and Hospital-acquired pneumonia. Infections are particularly severe in immunocompromised hosts, such as those undergoing Chemotherapy or Organ transplantation. The World Health Organization has classified ESBL-producing Enterobacterales as Priority pathogens for research and development of new antibiotics due to their critical threat level.

Treatment and management

Treatment is complicated by co-resistance to other antibiotic classes like Fluoroquinolones and Aminoglycosides. Carbapenems, such as Meropenem and Ertapenem, have traditionally been the drugs of choice for serious infections. However, rising Carbapenem resistance has driven the use of newer agents like Ceftazidime/avibactam, Cefiderocol, and Plazomicin. Alternative options for less severe infections may include Piperacillin/tazobactam or Temocillin, depending on local susceptibility patterns. Infectious Diseases Society of America guidelines emphasize the importance of Antimicrobial stewardship to optimize use of these critical agents.

Prevention and control

Prevention requires a multifaceted approach. Core Infection control measures include strict Hand hygiene compliance, contact Precautions for colonized or infected patients, and effective environmental cleaning. Antimicrobial stewardship programs are essential to reduce selective pressure by promoting appropriate antibiotic use. Surveillance cultures in high-risk units can help identify carriers. Research into Vaccine development against common ESBL producers and the use of Probiotics for decolonization are ongoing areas of investigation. Global initiatives like the World Health Organization's Global Antimicrobial Resistance and Use Surveillance System track the spread to inform public health policy.

Category:Antimicrobial resistance Category:Enzymes Category:Infectious diseases